Chapter 040. Diarrhea and Constipation (Part 6) doc

Diarrhea and Constipation Part 6 OTHER CAUSES Side effects from medications are probably the most common noninfectious cause of acute diarrhea, and etiology may be suggested by a temp

Chapter 040 Diarrhea and

Constipation

(Part 6)

OTHER CAUSES

Side effects from medications are probably the most common noninfectious cause of acute diarrhea, and etiology may be suggested by a temporal association between use and symptom onset Although innumerable medications may produce diarrhea, some of the more frequently incriminated include antibiotics, cardiac antidysrhythmics, antihypertensives, nonsteroidal anti-inflammatory drugs (NSAIDs), certain antidepressants, chemotherapeutic agents, bronchodilators,

antacids, and laxatives Occlusive or nonocclusive ischemic colitis typically

occurs in persons >50 years; often presents as acute lower abdominal pain preceding watery, then bloody diarrhea; and generally results in acute

inflammatory changes in the sigmoid or left colon while sparing the rectum Acute

diarrhea may accompany colonic diverticulitis and graft-versus-host disease

Acute diarrhea, often associated with systemic compromise, can follow ingestion

of toxins including organophosphate insecticides, amanita and other mushrooms, arsenic, and preformed environmental toxins in seafood, such as ciguatera and scombroid Conditions causing chronic diarrhea can also be confused with acute diarrhea early in their course This confusion may occur with inflammatory bowel disease (IBD) and some of the other inflammatory chronic diarrheas that may have

an abrupt rather than insidious onset and exhibit features that mimic infection

APPROACH TO THE PATIENT: ACUTE DIARRHEA

The decision to evaluate acute diarrhea depends on its severity and duration and on various host factors (Fig 40-2) Most episodes of acute diarrhea are mild and self-limited and do not justify the cost and potential morbidity of diagnostic or pharmacologic interventions Indications for evaluation include profuse diarrhea with dehydration, grossly bloody stools, fever ≥38.5° C, duration > 48 h without improvement, recent antibiotic use, new community outbreaks, associated severe abdominal pain in patients >50 years, and elderly (≥70 years) or immunocompromised patients In some cases of moderately severe febrile diarrhea associated with fecal leukocytes (or increased fecal levels of the leukocyte proteins) or with gross blood, a diagnostic evaluation might be avoided

in favor of an empirical antibiotic trial (see below)

Figure 40-2

Algorithm for the management of acute diarrhea Consider empirical Rx

before evaluation with (*) metronidazole and with (t) quinolone WBCs, white blood cells

The cornerstone of diagnosis in those suspected of severe acute infectious diarrhea is microbiologic analysis of the stool Workup includes cultures for bacterial and viral pathogens, direct inspection for ova and parasites, and

immunoassays for certain bacterial toxins (C difficile), viral antigens (rotavirus), and protozoal antigens (Giardia, E histolytica) The aforementioned clinical and

epidemiologic associations may assist in focusing the evaluation If a particular pathogen or set of possible pathogens is so implicated, then either the whole panel

of routine studies may not be necessary or, in some instances, special cultures may

be appropriate as for enterohemorrhagic and other types of E coli, Vibrio species, and Yersinia Molecular diagnosis of pathogens in stool can be made by

identification of unique DNA sequences; and evolving microarray technologies could lead to a more rapid, sensitive, specific, and cost-effective diagnostic approach in the future

Persistent diarrhea is commonly due to Giardia (Chap 202), but additional causative organisms that should be considered include C difficile (especially if

antibiotics had been administered), E histolytica, Cryptosporidium, Campylobacter, and others If stool studies are unrevealing, then flexible

sigmoidoscopy with biopsies and upper endoscopy with duodenal aspirates and biopsies may be indicated Brainerd diarrhea is an increasingly recognized entity characterized by an abrupt-onset diarrhea that persists for at least 4 weeks, but

may last 1–3 years, and is thought to be of infectious origin It may be associated with subtle inflammation of the distal small intestine or proximal colon

Structural examination by sigmoidoscopy, colonoscopy, or abdominal CT scanning (or other imaging approaches) may be appropriate in patients with uncharacterized persistent diarrhea to exclude IBD, or as an initial approach in patients with suspected noninfectious acute diarrhea such as might be caused by ischemic colitis, diverticulitis, or partial bowel obstruction